The differential producing Venturi has a long history of uses in many applications. With no abrupt flow restrictions, the Venturi can mix gases and liquids with a minimal total pressure loss. Recently, the Venturi has been used in carbureted engines. The suction from the throat of the Venturi provided the motive force for bringing the fuel in contact with the air. The improved application of the Venturi with the proposed invention is: the metering of the fuel is controlled by the fuel injector instead of the suction of the venturi; the fuel vaporization is facilitated by the reduced pressure in the throat of the Venturi; and mixing of the fuel/air mixture is further facilitated by the turbulent action in the outlet of the Venturi.
The principle behind the operation of the Venturi is the Bernoulli effect. The Venturi mixes vapors and liquids by reducing the cross sectional flow area in the air flow path, resulting in a pressure reduction in the throat of the Venturi. After the pressure reduction, the mixture is passed through a pressure recovery exit section where most of the pressure reduction is recovered. The pressure differential follows Bernoulli's Equation, simplified for a negligible change in elevation:P1+½d1v12=P2 +½d2v22 where,    P1=Pressure at the inlet of Venturi (FIG. 1, location 1);    P2=Pressure at the throat of the Venturi (FIG. 1, location 2);    d1=air density at the inlet of the Venturi (FIG. 1, location 1);    d2=air density at the throat of the Venturi (FIG. 1, location 2);    v1=air velocity at the inlet of the Venturi (FIG. 1, location 1) and; −v2=air velocity at the throat of the Venturi (FIG. 1, location 2).
In FIG. 1, the air enters the Venturi at the location 1 with a cross-sectional area A1, pressure P1, and velocity v1. These properties form the potential and kinetic energy of the fluid at one location. Energy is conserved in a closed system, that is, the sum of potential and kinetic energy at one location must equal the sum of the potential and kinetic energy at any another location in the system. If potential energy decreases at one location, the kinetic energy must proportionally increase at that location. The fluid enters the throat of the Venturi at location 2 with a new area A2, which is smaller than A1. In a closed system mass can be neither created nor destroyed (law of conservation of mass), and as such, the volumetric flow rate at area A1 must equal the volumetric flow rate at area A2. If the area at location A2 is smaller than A1, the fluid must travel faster to maintain the same volumetric flow rate. This increase in velocity results in a decrease in pressure according to the Bernoulli's equation.